Besides one being made from clay and one from concrete there are a number of differences between the two.
As clay is a natural material, the colour is inherent within it; consequently, exposure to Ultra Violet light will not have an effect on the vibrancy of the colour over time.
Concrete however, is a pigmented material and over time and exposure to UV light there will be a reduction in the intensity of colour, this will not be a noticeable change due to the length of time it will take.
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